Tri-calcium phosphate and aluminum phosphate composition salt filler



tri-calcium phosphate.

Patented July 5, 1932 f T STA Parent WILLIAM enonen wannine AND rnnononn WILLIAM smarts, orsr. LOUIS, Mrs SOURI, assreuons TO swarm :ansnenon, 11m, A. CORIPORATION or ALABAMA anathema rnosrnn'rn Ann ALUMINUM PHOSPHATE comrosrrrou SALT FILLER N0 Drawing.

1f the tendency of the salt to cake. Caking is very objectionable in a product intended for these purposes. The fillers which have found extensive use are :-sodium bicarbonate, magnesium carbonate, di-calcium phosphate and From 0.5% to 1.5% of these substances are incorporated in fine -salt'producing a product which is relatively free flowingand subject tostorage Without calring as compared with the untreated salt.

'Magnesium carbonate and tri-calcium phosphate are more generally used. These substances may also be applied to other crystalline or granular products where a reduction in a tendency to cake is desired.

Thisinventionhas as an object a new com position of matter superior in caking inhibiting properties to t-hose now in common use.

A furtherobject is an improvement in tricalcium phosphate which renders it more 9 effective in inhibiting caking in crystalline or granular substances.

" These objects are accomplished by the following invention which sets forth a compo- SltlOIl of matter consisting of tri-calcium phosphate and aluminum phosphate. It is common knowledge that when milk of lime f is precipitated with phosphoric acid the V precipitate is more basic than normal tri-calcium phosphate (3CaO.P O A compound '49. corresponding to the formula soarronao onya on account of adsorbed lime. In the de- Application filed September 3, 1929. Seria1No.390,208.

scription of thisinvention, therefore, We do not intend to limit ourselves by the use of the term tri-calcium phosphate to the definite compound'3CaO.P Q but desire it to hennderstood that this term is used to. include phosphates of lime having a molecular ratio of 3 or moremolecules of CaO to one molecule OfP O We have found that for inhibiting caking in salt, tri-calcium phosphate may be materially improved if it contains 4% to 20% aluminum; phosphate f (AlPO a preferred amount being 7%. The aluminum phosphate may be incorporated in the tri-calcium phosphate in any convenient manner which may readily suggestitselfto those versed in the art of. chemical manufacture.

toxide (P 0 as phosphoric acid diluted to 16 pounds granular metallic 22 Baum. aluminumor 47 lbs. purifiedbauxite are dissolved in a portion of this acid, equivalent to l68pounds'P O The resulting acid solution of aluminum phosphate (AlPOQ is filtered free ofinsoluble materialand mixed with theremainder of the original batch-of acid. The combined acid mixture is fed with agitation into a milk of lime containing437 pounds 'calcium'oxide (CaO) at a concentration of approximately l05 grams CaO per liter.) The additionof theiacid mixture is continued until a 10 cc. sample of the slurry requires 2 cc. of 0.1 N alkali to bring. to alkaline penolphthalein end point. Stirring is continued two hours to complete the reaction and then the slurry may be filtered and dried in the conventional manner or it may bedried by atomizing in a current of warm air. Thedried product which still contains 10% to 15% water as determined by. ignition'loss mustt-hen be ground toreduce the" particles to a sufficient degree of fineness (1 to l -microns). We have found an attrition mill; to be a suitable type for this reduction.

A typical analysis of the product produced by this procedure is as follows? I I Per: cent CaO 4A4 P 38.1 AlPO r 7. 12

y We have" found that other metallic phos- I phates such as iron may also be used to. enhance the caking inhibit ng properties of tri-calciimi phosphate but due to the fact" that they impart objectionable colors to the finished product they are undesirable for this purpose.

Finely ground tri-calcium phosphate containing 4c%v to 20% aluminum phosphate may be. advantageously mixed tothe extent of stantial1y.1% er a caking inhibitor consisting essentially of tri-calcium phosphate containing approximately 7% aluminum phosphate,

4:. Dry sodium chloride containing a caking inhibitor consisting offin'ely ground tricalcium phosphate with aluminum phosphate 7 I 7111 excess of 4%. r

5. A1 dry salt'containing a filler consisting of finely ground tri-calcium phosphate with4% to 20% aluminum phosphate.

6. A dry salt containing a caking inhibitor consisting of finely ground tri-calcium phosphate containing 7% aluminum phosphate. 7 In testimony whereof they affix their signatures.

WILLIAM GEORGE WARNING- THEODORE WILLIAM SCHILB.

1% with fine table salt or salt prepared for a self risingfiour manufacture to prevent caking. It may also be used with other crystal- 25' line or granular materials such as mono-calcium phosphate to. reduce a tendency toward caking.

an oven at"10 0 F. for 30 minutes. The comparative degree of caking in the samples of salt wasdetermined and; it was found that the specially prepared tri-c'alcium phosphate containing 7% aluminum phosphate ranked first as a caking inhibitor with magneslum carbonate second, ordinary tr1-cal- "ci um phosphate third, sodium bicarbonate fourth and di-calcium phosphate fifth. V

. It is known that aluminum phosphate is presentto a limited extent in tri-calcium phosphate as ordinarily manufactured being I 1 included as an unavoidable impurity in the phosphoric acid .but the quantities usually.

present (0.2% to 2.0%) are not suflicient to accomplish the improvement in cakingfin hibiting properties gained by our invention.

Having'described the properties of our invention, its application, and. a convenient method ofjmanu-facture, whatwe claim as I new andnovel is:-

, 1. A, dry salt containing up to 1%. of} a filler consisting of tri-calcium phosphate with aluminum. phosphate excess of 74% 2. Dry sodium chloride containing approximately 1% of' a filler consisting of tril-cal- Y ci'um phosphate and 4%. to20.% aluminum phosphate. 1

3'; Dry sodium chloride containing sub- 

